In conventional data processing systems including a plurality of data processors which communicate with one another, such communication is often controlled by an interrupt mechanism. For example, if a first data processor wishes to communicate with a second data processor, the first data processor applies to the second data processor an interrupt signal which interrupts the second data processor. Conversely, if the second data processor wishes to communicate with the first data processor, then the second data processor applies to the first data processor an interrupt signal which interrupts the second data processor. Each of the data processors typically includes an interrupt service routine which then handles the requested communication.
Execution of the interrupt service routines disadvantageously adds overhead processing to the processing loads of the data processors. In addition, servicing an interrupt can be particularly disadvantageous if the interrupted data processor has a pipelined data processing architecture.
It is therefore desirable to reduce the amount of interrupt activity involved in controlling communications between data processors.
According to the invention, a first data processor will interrupt a second data processor for communication therewith only if the first data processor determines that I/O is blocked on the second data processor. By using the indication of whether or not I/O is blocked on the second data processor, the first data processor can advantageously avoid interrupting the second data processor unnecessarily.